IGF-1 LR3

Muscle Research only Animal studies

Also called Long R3 IGF-1, Long Arg3 IGF-I

A lab-made version of insulin-like growth factor 1, rebuilt with a 13-amino-acid extension and one substitution so it mostly escapes the binding proteins that normally mop up IGF-1. The result stays active far longer than the natural hormone.

Evidence at a glance

Evidence: Animal studies — Not yet studied in people
Status: Research compound only
Dosing: No human study has set a dose

Essentially all data is cell culture, where it is sold as a laboratory reagent. IGF-1 signalling drives cell growth broadly, so sustained elevation carries a real theoretical cancer concern, and it can cause low blood sugar.

What studies report

Potent activation of the IGF-1 receptor in cultured cells
Longer activity than native IGF-1 because it evades IGF-binding proteins
Standard reagent for serum-free cell culture

How it works

Activates the IGF-1 receptor like native IGF-1, but a 13-residue extension and an arginine substitution stop it binding the IGF-binding proteins that would normally sequester it — so far more of it stays free and active.

Binds a receptor on the cell surface and signals inward

Where it acts

Skeletal muscle

The library groups this compound under Muscle. The diagram shows that target, not every tissue it reaches.

Illustrated

Close-up skeletal muscle satellite cell nestled beside a muscle fibre under a thin basal lamina.

AI-generated subject illustration; not a depiction of the compound or evidence of its effects.

Why people take it

Muscle growth and hyperplasiaRecovery from trainingNutrient partitioning

Reasons people seek it out — not a list of proven effects.

In practice Unapproved use

Used in bodybuilding, typically post-workout and in short runs
Short runs are deliberate — the community treats long exposure as risky

Reported real-world use, not evidence and not a recommendation.

Dosing

No human study has established a dose for this compound.

What people report using Not evidence

20–50 mcg daily post-workout, in short runs

Sold as a cell-culture reagent. There is no human dosing literature, and hypoglycaemia is a real acute risk.

Reported for reference, not as instruction. Nothing here is a recommendation to take anything, and most of these compounds are not approved for human use.

Status: Sold as a cell-culture reagent. Not approved for human use.

Route: Subcutaneous injection, from reconstituted lyophilised powder
Molecular weight: 9111.5 (≈9.1 kDa)
CAS: 143045-27-6
Available as: 10 mg

Search PubMed for IGF-1 LR3 → We link a live search rather than a fixed citation list, so it stays current and nothing here is a reference we have not checked.

Educational information only. Nothing here is medical advice, a dosing protocol, or a recommendation to use any compound. Most entries describe substances not approved for human use. Talk to a licensed clinician before acting on anything you read here. How to read these entries.